This invention relates to a shift device for a marine propulsion and more particularly to an improved shifting mechanism for a transmission.
In one widely used form of transmission, which is used principally in the forward, neutral, reverse transmission of a marine outboard drive, there are a pair of counter-rotating bevel gears that are journaled relative to the shaft to be driven. A dog clutching element is supported between these gears and has dog clutching teeth that are adapted to engage with corresponding dog clutching teeth of selected ones of the gears for rotatably coupling that gear to the driven shaft.
Although this type of transmission has the advantage of extreme simplicity, the engagement of the dog clutching elements can give rise to noise and also can be otherwise difficult to make shift smoothly. Therefore, it has been proposed to employ some form of spring mechanism in the actuator for the dog clutching element so as to reduce shock. In addition, a detent mechanism may cooperate with the spring so as to permit loading of the spring until the detent releases and then effect snap engagement of the dog clutching elements.
The use of such an arrangement has advantages, however, the use of the single spring arrangement for effecting both snap action and for cushioning the engagement can give rise to certain difficulties and compromises. With such an arrangement it may be important to provide a delicate adjustment of the preloading of the spring and normally two springs may be employed for this purpose, thus complicating the preloading of the springs. This is particularly important in connection with marine transmissions since the construction is very compact but nevertheless employs a large number of components.
It has also been proposed to employ separate spring arrangements for achieving the snap action and the cushioning operation, but the devices of this type have been rather complicated and, in many instances, only provide spring cushioning in one direction of movement. If spring action is provided in both directions, the previously proposed devices have necessitated the use of a multiplicity of springs.
It is, therefore, a principal object of this invention to provide an improved shifting device for a transmission.
It is a further object of this invention to provide an improved shifting device for the dog clutching element of a transmission.
It is a further object of this invention to provide an improved shifting and cushioning arrangement for a transmission of the type normally used in marine propulsion units.